lncRNA TM4SF1-AS1 predicts dismal outcomes and promotes cholangiocarcinoma progression via modulating miR-744-3p.

BACKGROUND: Cholangiocarcinoma (CCA) is of great malignancy and high mortality. Identification of effective biomarkers could improve the monitoring of CCA development and attenuate patients' outcomes. OBJECTIVE: The potential of lncRNA TM4SF1-AS1 (TM4SF1-AS1) serving biomarker of CCA was estimated and the underlying mechanism was also investigated. METHODS: A total of 107 pairs of tumor and paracancer tissues were collected from CCA patients. The expression levels of TM4SF1-AS1 and miR-744-3p were analyzed in CCA by PCR, and their clinical significance was estimated by a series of statistical analyses. CCK8 and Transwell assays were used to assess the development-related cellular processes of CCA. The interaction between TM4SF1-AS1 and miR-774-3p was evaluated by cell transfection and dual-luciferase reporter assay. RESULTS: The elevated expression of TM4SF1-AS1 and the declined expression of miR-744-3p were observed in CCA. Both TM4SF1-AS1 and miR-744-3p were found to possess a close association with the malignant progression and poor prognosis of CCA patients. TM4SF1-AS1 was suggested to act as a tumor promoter of CCA, where miR-744-3p was found to mediate the function of TM4SF1-AS1. CONCLUSION: Both TM4SF1-AS1 and miR-744-3p were identified as prognostic biomarkers of CCA. TM4SF1-AS1 served as tumor promoter of CCA via modulating miR-744-3p.

Immune Infiltration and Clinical Outcome of Super-Enhancer-Associated lncRNAs in Stomach Adenocarcinoma.

Super-enhancers (SEs) comprise large clusters of enhancers that highly enhance gene expression. Long non-coding RNAs (lncRNAs) tend to be dysregulated in cases of stomach adenocarcinoma (STAD) and are vital for balancing tumor immunity. However, whether SE-associated lncRNAs play a role in the immune infiltration of STAD remains unknown. In the present study, we identified SE-associated lncRNAs in the H3K27ac ChIP-seq datasets from 11 tumor tissues and two cell lines. We found that the significantly dysregulated SE-associated lncRNAs were strongly correlated with immune cell infiltration through the application of six algorithms (ImmuncellAI, CIBERSORT, EPIC, quantiSeq, TIMER, and xCELL), as well as immunomodulators and chemokines. We found that the expression of SE-associated lncRNA TM4SF1-AS1 was negatively correlated with the proportion of CD8+ T cells present in STAD. TM4SF1-AS1 suppresses T cell-mediated immune killing function and predicts immune response to anti-PD1 therapy. ChIP-seq, Hi-C and luciferase assay results verified that TM4SF1-AS1 was regulated by its super-enhancer. RNA-seq data showed that TM4SF1-AS1 is involved in immune and cancer-related processes or pathways. In conclusion, SE-associated lncRNAs are involved in the tumor immune microenvironment and act as indicators of clinical outcomes in STAD. This study highlights the importance of SE-associated lncRNAs in the immune regulation of STAD.

Effect and mechanism of downregulating the long-chain noncoding RNA TM4SF1-AS1 on the proliferation, apoptosis and invasion of gastric cancer cells.

BACKGROUND: To investigate long-chain noncoding TM4SF1-AS1 in gastric cancer (GC) tissues and cells. METHODS: TM4SF1-AS1 in 40 GC tissues and adjacent tissues was detected and compared using real-time fluorescence quantitative PCR (qRT-PCR). TM4SF1-AS1 in MKN28 and SGC7901 GC cells was downregulated using small interfering RNA (shRNA). The cells were grouped into an interference group (shTM4SF1-AS1 group) and a control group (shControl group). MTT and Transwell tests were applied to determine the proliferation and invasion of the cells in both groups, and flow cytometry was performed to assess the apoptosis rate in the two groups. Western blotting was performed to determine changes in key proteins in cells during the epithelial-to-mesenchymal transition (EMT) and in the TM4SF1 and PI3K-AKT signalling pathways in response to the downregulation of TM4SF1-AS1. RESULTS: The proliferation of MKN28 and SGC7901 in the shTM4SF1-AS1 group was significantly inhibited at 48 h and 72 h compared to that in the shControl group (all P < 0.05). In the shTM4SF1-AS1 group, the number of invaded MKN28 and SGC7901 cells was significantly lower than that in the shControl group (all P < 0.05). Apoptosis in the MKN28 and SGC7901 shTM4SF1-AS1 groups was significantly higher than that in the shControl group (all P < 0.05). Compared to those in the shControl group, levels of E-cadherin in EMT-related proteins were significantly elevated (P < 0.01), while levels of N-cadherin, Snail and Twist1 were significantly decreased (all P < 0.01). After silencing the expression of LncTM4SF1-AS1, the expression levels of TM4SF1 in the shTM4SF1-AS1 group were downregulated compared to those in the shControl group, and the p-PI3K and p-AKT proteins in the PI3K-AKT signalling pathway in the shTM4SF1-AS1 group were downregulated compared to those of the shControl group. CONCLUSIONS: TM4SF1-AS1 is upregulated in gastric cancer tissues and cells. Interfering with and downregulating its expression inhibit cancer cell proliferation, invasion and the EMT and promote apoptosis. The underlying mechanism for these effects is related to silencing the TM4SF1 and PI3K-AKT signalling pathways. TM4SF1-AS1 may be a potential therapeutic target for gastric cancer.

HIF-1α-activated TM4SF1-AS1 promotes the proliferation, migration, and invasion of hepatocellular carcinoma cells by enhancing TM4SF1 expression.

Long non-coding RNAs (lncRNAs) are essential drivers or suppressors in human hepatocellular carcinoma (HCC) by participating in controlling transcription, translation, mRNA stability, and protein degradation protein-protein interaction. TM4SF1-AS1 is recently identified as a tumor-promoting factor in lung cancer. Nevertheless, its function in HCC and related molecular mechanisms remain unknown. Here, our data indicated that either hypoxia or hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor (DMOG) induced the upregulation of TM4SF1-AS1 in HCC cells. HIF-1α knockdown rather than HIF-2α silencing remarkably abrogated hypoxia-upregulated TM4SF1-AS1 expression. Furthermore, we confirmed the elevated expression of TM4SF1-AS1 in HCC tissue samples and cell lines. The silencing of TM4SF1-AS1 prominently inhibited the proliferative, migratory, and invasive abilities of HCC cells. TM4SF1-AS1 depletion significantly blocked hypoxia-enhanced Hep3B cell proliferation and mobility. Interfering TM4SF1-AS1 remarkably reduced TM4SF1 mRNA and protein levels in HCC cells. But TM4SF1-AS1 knockdown did not impact the stability of TM4SF1 mRNA. Hypoxia enhanced the expression of TM4SF1 mRNA, which was subsequently decreased by TM4SF1-AS1 knockdown in HCC cells. We confirmed the positive correlation between TM4SF1 mRNA and TM4SF1-AS1 expression in HCC specimens. Finally, TM4SF1 prominently reversed the inhibitory role of TM4SF1-AS1 depletion in Hep3B cells. In summary, hypoxia-responsive TM4SF1-AS1 was overexpressed in human HCC and contributed to the malignant behaviors of tumor cells by enhancing TM4SF1-AS1 expression.

lncRNA TM4SF1-AS1 Activates the PI3K/AKT Signaling Pathway and Promotes the Migration and Invasion of Lung Cancer Cells.

PURPOSE: Metastasis is a crucial cause of the high mortality in patients with lung cancer. Long non-coding RNAs (lncRNAs) are emerging as important players in the development and progression of human cancers. Here, we aimed to identify metastasis-associated lncRNA and to study its roles in the migration and invasion of lung cancer cells. MATERIALS AND METHODS: We screened differentially expressed lncRNAs between high- and low-metastatic lung cancer cell lines by using microarray and identified the target lncRNA TM4SF1-AS1. The effect of the TM4SF1-AS1 on the invasion and migration was evaluated through the wound healing experiment and transwell assay. The expression of related genes was assessed by RNA sequence and Western blotting. RESULTS: TM4SF1-AS1 was highly expressed in high metastatic lung cancer cell line, and it was also significantly up-regulated in lymph node metastatic lung cancer and was associated with lymph node metastasis. Overexpression of TM4SF1-AS1 promoted the migration and invasion of lung cancer cells. Overexpression of TM4SF1-AS1 decreased the expression of E-Cadherin and increased the expression of Vimentin, Snail and Twist, while knockdown of TM4SF1-AS1 exhibited the opposite trend. Furthermore, RNA sequence analysis revealed that some signaling pathways, including PI3K/AKT signaling pathway, were enriched upon TM4SF1-AS1 overexpression. Western blotting further confirmed that the PI3K/AKT signaling pathway was activated by TM4SF1-AS1. CONCLUSION: This study illustrates that TM4SF1-AS1 promotes the migration and invasion of lung cancer cells by activating the PI3K/AKT signaling pathway. TM4SF1-AS1 might be a novel target of molecular treatment for lung cancer.